JP2006019465A - Semiconductor package and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor package which can easily form a solder fillet in a surface mounting type package and can raise the solder adhering strength of a substrate to the package, and to provide a method of manufacturing the same. <P>SOLUTION: The semiconductor package 1 is a semiconductor package which seals leads except a terminal. The leads each has an external terminal 3 extended in parallel with a substrate surface to be mounted. The external terminal has a recess 4 passing the upper surface and the lower surface of the external terminal without including the side of a section in the section of the extending direction tip end. The recess is plated. The method of manufacturing the semiconductor package includes an inserting step of previously inserting a lead frame having a through hole into a mold at the external terminal of the lead, a molding step of injecting a resin and molding it, a plating step of plating the lead frame exposed part, and a cutting step of cutting the lead frame. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor package in which leads are sealed leaving a terminal portion and a method for manufacturing the same. More particularly, the present invention relates to a surface-mount type semiconductor package that can easily form a solder fillet and a method for manufacturing the same.

  It is known that a semiconductor element is greatly affected by changes in ambient temperature and humidity, or fine dust and dust, and its characteristics are deteriorated, and it is easily damaged due to mechanical vibration and impact. In order to protect the semiconductor element from these external factors, it is well known that the semiconductor element is sealed with a ceramic box or resin and used as a package.

  Above all, solid-state image sensors such as CCD and CMOS, laser elements such as LD and PD, and photodiode elements need a light path with the outside of the package. It cannot be sealed with resin or ceramics. These semiconductor elements are generally packaged by being mounted in a hollow type package in which one side is opened, and then the open part is sealed with a transparent material such as glass.

  On the other hand, in recent years, electronic devices are required to be reduced in size and thickness, and the above-described sealed type semiconductor package and hollow type package are also required to be reduced in thickness and size. As one of the solutions, a surface mount type package in which external terminals are provided in a direction parallel to the substrate from the bottom surface of the package has been put into practical use. As this type of package, SON (Small Outline Non-Lead Package), QFN (Quad Flat Non-Lead Package), and the like are known.

  Unlike the DIP (Dual Inline Package) and SOP (Small Outline Package), the surface mount type package does not have "foot" (external terminal in the direction perpendicular to the board) when mounting, so mounting by hand solder is difficult. In general, flow soldering and reflow soldering are often used.

For example, in the case of reflow soldering, solder is usually deposited not only in the lower part of the external terminal but also in the space around the terminal. The solder piled up around the terminals is called a solder fillet and functions to increase the solder bonding area and the mounting strength. In order to form a solder fillet, a high solder wettability plating (gold plating or the like) is applied to the lower and side surfaces of the terminal so that the corresponding part is more firmly bonded to the solder. (See Non-Patent Document 1)
Compared with a ceramic package, a resin semiconductor package cannot be gold-plated on a cut surface of an external terminal because of its manufacturing method. Therefore, there is a problem that it is difficult to form the solder fillet because the solder does not get on the terminal cut surface.

  Now, in the case of a solid-state imaging device package such as a CCD or CMOS, there has been a problem of heat resistance such as the chip itself or a color filter, and the flow solder and reflow solder mounting that heats the whole package causes a problem. In many cases, manual solder mounting was performed. However, in response to the recent demand for thinning, when trying to fabricate a solid-state imaging device package using thin resin SON, QFN, manual soldering is difficult, so mounting method by reflow soldering, especially for the device A reflow mounting method using low-temperature solder is being used so as not to cause damage.

  When such a low-temperature solder is used, since the solder adhesive strength is inferior to that of normal solder, a resin package in which a solder fillet cannot be formed has a problem that the adhesive strength between the substrate and the package is low. . In addition, CCD elements and color filters have been improved, and heat resistance has increased, so normal reflow solder mounting (mounting at a temperature of about 230 ° C) and lead-free solder mounting, which will be a low environmental load in the future (Mounting at a temperature of about 260 ° C.) is also being performed, and it is an issue to increase the adhesive strength by forming a solder fillet.

  In order to solve this problem, Patent Document 1 and Patent Document 2 make proposals to increase the spread of solder fillets. In Patent Document 1, an attempt is made to widen the solder fillet by increasing the thickness of the outer lead. However, since the entire package becomes thicker or a lead frame having a different thickness needs to be prepared, it can be applied to any package. There is a problem that does not mean. Patent Document 2 proposes to cut the outer lead in an oblique direction. However, there is a possibility that a thinly cut portion may be bent weakly in strength, or a special cutting device is required. Because it becomes, it is not realistic.

Yoshikazu Tanaka, “Soldering Technology”, General Electronic Publishing Company, July 20, 1974, first edition Japanese Patent Laid-Open No. 10-270628 JP 2004-87798 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor package and a method for manufacturing the same that can easily form a solder fillet in a surface-mount package and can increase the solder bond strength between the substrate and the package.

  The semiconductor package of the present invention is a semiconductor package in which leads are sealed leaving a terminal portion, and the leads have external terminals extending in parallel to a substrate surface to be mounted. The cross section of the front end portion in the extending direction has a concave portion penetrating the upper surface and the lower surface of the external terminal without including the side of the cross section, and the concave portion is plated.

The method of manufacturing a semiconductor package according to the present invention, in manufacturing a semiconductor package in which leads are sealed leaving a terminal portion,
Insert step of inserting a lead frame having a through hole in advance into a die in an external terminal portion of the lead,
A molding process in which resin is injected and molded;
It includes a plating step of plating the exposed portion of the lead frame and a cutting step of cutting the lead frame across the through hole of the external terminal portion.

  According to the present invention, when mounting a surface-mount type semiconductor package on a substrate, the inner surface of the recess has a recessed portion plated with solder, so that the inner surface of the recessed portion is wetted by solder when soldered. This facilitates the formation of a solder fillet at the tip of the external terminal. As a result, for example, even when mounting using low-temperature solder, mounting with excellent adhesion strength to the substrate is possible.

  The semiconductor package of the present invention is made of a sealing material such as a resin composition and a conductive lead, and an external terminal serving as an electrical contact with the substrate is produced from the lead, and the external terminal is mounted on the surface of the substrate to be mounted. It extends in the parallel direction, and the cross section of the tip part penetrates the upper surface and the lower surface of the external terminal without including the side of the cross section, as viewed from the upper surface, a semi-elliptical shape, a semicircular shape, a U-shape, A semiconductor package having concave portions such as a quadrangular shape and a triangular shape, wherein the upper surface, the lower surface, and the side surfaces of the external terminals and the wall surfaces of the concave portions are plated.

  As a resin material for sealing a semiconductor package, a so-called semiconductor sealing material obtained by kneading silica as a filler in an epoxy resin and a phenol resin can be preferably used. And Sumitomo Bakelite's Sumicon EME series. Needless to say, this is only an example, and any type of resin can be used depending on the intended use of moisture resistance as long as it can be integrally formed with the lead frame.

  A schematic plan view of an example of a package according to the present invention is shown in FIG. This example is a hollow package 1 having an internal terminal 2 and an external terminal 3, and the wall surface of the recess 4 at the tip of the external terminal is plated. Therefore, when solder mounting is performed, this portion is also wetted by the solder, so that the concave portion is soldered to the substrate. For this reason, conventionally, solder has not been applied to the cross section of the tip of the external terminal, but a solder fillet can be formed by this method.

  Here, the type of plating applied to the recess can be appropriately selected depending on the type of lead frame metal used, the type of solder, and the like. Usually, a 42 alloy and a copper alloy are often used for the lead frame, and since it is often mounted with a tin / lead solder, a base nickel plating or a surface gold plating is selected as the plating. Separately, it can be employed according to applications such as solder plating and palladium plating. The plating thickness is selected according to the application. In general, when the base is nickel plating, the nickel layer is 1 μm to 20 μm, preferably 3 μm to 10 μm, and the gold plating on the surface is 0.1 μm to 1 μm, preferably 0.1 μm to 0.5 μm is selected.

As a method for manufacturing a semiconductor package of the present invention, a lead frame used for manufacturing a semiconductor package in which leads are sealed leaving a terminal portion, at a position corresponding to an external terminal, at a cutting position of the lead frame, Insert step of inserting at least the lead frame into a mold using a lead frame having a through-hole such as a circular shape, an elliptical shape, a long hole shape, a rhombus shape, a square shape in advance,
A molding process in which resin is injected and molded;
It includes a plating step of plating the exposed portion of the lead frame and a cutting step of cutting the lead frame across the through hole of the external terminal portion.

  In an ordinary surface mount package manufacturing method, the external terminals and the lead frame are separated in a cutting step after the plating step. Therefore, since the cut surface is not plated, it is difficult to form a solder fillet. On the other hand, since the insert type package (for example, DIP or SOP) has “foot”, the soldered fillet can be formed because it is joined with the plated foot after cutting.

  Therefore, according to the manufacturing method of the present invention, a concave portion can be provided on the end surface of the external terminal, and plating can be applied to this wall surface. FIG. 2 shows a schematic plan view of an example of a package obtained by the manufacturing method of the present invention in a state where it is connected to a lead frame before the package is singulated. This example is a hollow package 1 having an internal terminal 2 and an external terminal 5 before cutting, and a through hole 6 is formed in a cut portion 7 of the external terminal, and the inner wall surface of the through hole is plated. Thereby, the recessed part by which plating was given to the external terminal front-end | tip part after a cutting | disconnection is formed.

  Although the present invention has been described with respect to a hollow package for semiconductor mounting, it is needless to say that the package has the same shape and can be applied to other packages as long as the package is solder-mounted on a substrate. It is. For example, full-mold type surface mount packages such as DRAM, power transistor packages, etc., and examples of hollow packages include LDs, optical packages with LED elements, pressure sensors, piezoelectric sensors, gyro sensors, temperature sensors It can also be applied to MEMS packages such as capacitors and micromotors.

Although the package excellent in solder mounting property obtained by the present invention will be specifically described below, the present invention is not limited to the following.
[Example 1]
A lead frame having a thickness of 0.15 mm having a circular through hole was previously placed in a mold at a position corresponding to the external terminal at the cutting position of the lead frame, and a resin package was molded.
A resin tablet obtained by compressing granules of an epoxy resin composition (TM-250G manufactured by Mitsui Chemicals, Inc.) was injected into a mold under the conditions of a mold temperature of 160 ° C. and an injection pressure of 1.5 MPa. A SON (Small Outline Non-Lead Package) type semiconductor package shown in FIG.

After that, the entire lead frame including the through hole is plated in the order of nickel plating (thickness 5 μm) and gold plating (thickness 0.3 μm), and the lead is crossed through the through holes previously formed in the lead frame. The frame was cut to obtain an individual package.
The obtained package was placed on a substrate coated with a solder paste, and solder reflow mounting at 230 ° C. was performed under a nitrogen stream.

  After mounting, the solder fillet height was measured. The fillet height is the ratio of the fillet height to the lead height (f / h) × 100 (where h is the height of the package external terminal (outer lead) and f is the fillet height at the outer lead tip. %). The results are shown in Table 1. FIG. 4 is an enlarged side view of the external terminal portion showing the relationship between the fillet height f and the external terminal height h.

[Example 2]
A package was prepared in the same manner as in Example 1 except that the thickness of the lead frame used was 0.20 mm, and the fillet height ratio was similarly determined.

[Comparative Example 1]
A package was prepared in the same manner as in Example 1 except that a 0.15 mm thick lead frame having no through hole at the cutting position was used, and the fillet height ratio was similarly determined.

  As shown in the results of Table 1, it was found that by using the present invention, a solder fillet can be effectively formed for a surface mount package.

  The surface-mount type semiconductor package of the present invention can effectively form a solder fillet at the tip of the external terminal, which has been considered difficult in the past, and in particular, a semiconductor package with excellent adhesion strength to the substrate is manufactured. For example, the reliability of the package can be improved in low-temperature solder mounting with low solder strength or reflow mounting. Therefore, the present invention can also be applied to other packages such as an optical package on which an LD or an LED element is mounted, a MEMS package such as a pressure sensor, a piezoelectric sensor, a gyro sensor, a temperature sensor, a capacitor, or a micromotor.

It is a schematic plan view of an example (SON type hollow package) of the package by this invention. It is a schematic plan view which shows the state before dividing into an example of the package obtained by the manufacturing method of this invention. The top view of the package (SON type | mold hollow package) manufactured in the Example of this invention is shown. It is a side surface enlarged view of the external terminal part which shows the relationship between fillet height f and the height of an external terminal h.

Explanation of symbols

1 Package 2 Internal terminal (Inner lead)
3 External terminal (outer lead)
4 Recess 5 External terminal (before cutting with lead frame)
6 Through-hole 7 Cutting part 8 Substrate 9 External terminal 10 Solder fillet

Claims (2)

  A semiconductor package in which a lead is sealed leaving a terminal portion, and the lead has an external terminal extending in parallel to a substrate surface to be mounted, and the external terminal is a cross-section of a tip portion in the extending direction. And a recess that penetrates the upper surface and the lower surface of the external terminal without including the side of the cross section, and the recess is plated. In manufacturing a semiconductor package in which leads are sealed leaving a terminal portion,
Insert step of inserting a lead frame having a through hole in advance into a die in an external terminal portion of the lead,
A molding process in which resin is injected and molded;
A method of manufacturing a semiconductor package, comprising: a plating step of plating the exposed portion of the lead frame, and a cutting step of cutting the lead frame across the through hole of the external terminal portion.

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